Method of making glass reinforced plastic articles



Feb. 10, 1959 D. N. DAVIES ET AL 7 METHOD OF MAKING GLASS REINFORCEDPLASTIC ARTICLES Filed Feb. 4, 1955 FIG. I

INVENTORS' DRURY NORMAN DAVIES 8. LESLIE FRANCIS BULL BYWM M+ MATTORNEYS United States Patent Englefield Green, and Leslie London,England, assignors to Limited, Edinburgh, Scotland,

Drnry Norman Davies,

Francis Bull, Southgate, The Distillers Company a British companyApplication February 4, 1955, Serial No. 486,228

Claims priority, application Great Britain February 11, 1954 l 8 Claims.(Cl. 15483) The present invention relates to improvements in or relatingto the production of reinforced plastic articles. In particular itrelates to articles made from glass fibres and filaments bonded togetherwith a laminating composition comprising an unsaturated polyesterresinmixed with a monomeric styrene compound. By styrene compound is meantthroughout this specification styrene or a polymerisable derivativethereof. Examples of such compounds include the vinyl toluenes,u-methylstyrene, the ethyl substituted styrenes and the monoanddichlornuclear substituted styrenes.

It is known to use glass fibres and filaments in the form of yarns,rovings, mats and fabrics in theproduction of reinforced plasticarticles in which the laminating compositions comprise unsaturatedpolyester resins mixed with monomeric styrene compounds. Such articleshave excellent mechanical properties combining high tensile strengthswith low densities.

A procedure for preparing such articles is the lay-up technique in whichthe glass fibres, in the form of mats, rovings or woven fabric, arebonded togetherwith laminating compositions in syrup form and shaped ina female mould or on a male mould, the mould being removed after theresin has set, to produce a rigid article whose shape on one side atleast is an accurate replica of the mould surface. If the shape of themould surface is such as to present undercuts it is often necessary totake special measures to permit the removal of the mould from the rigidshaped article. For instance female moulds may be made in two or moresections which are screwed or otherwise fastened together in order tofacilitate the removal of the article. In the case of male moulds, especially when the mould is cylindrical, spherical or bottle shaped, thespecial measures taken to ease the final removal of the mould are evenmore complex and require the use of, for instance, moulds having slidingtapered members or having segments of fusible material, for example, waxor low melting point resins or metals, which can be subsequently meltedto allow removal of the mould from the finished article.

The difiiculty of the separation of the finished article from the mouldis often present in the manufacture of tubular shaped articles bywinding glass fibres around a mandrel and bonding them by means of alaminating composition. The cure of the laminating composition ofteninvolves some contraction and consequently it is often impossible toremove the finished article from the mandrel owing to the frictionalforces set up between them.

In the case of hollow articles of spherical or bottle shape made by thebuilding up of bonded glass fibres around a male former, nothing shortof complete disintegration of the. former may be sufiicient to enable itto be removed.

Special measures such as those outlined above involve high costs in theproduction of moulds and in their operation.

i take place.

An object of the present invention is to provide a process for themanufacture of reinforced plastic articles in which the above-mentioneddifiiculties do not arise.

Accordingly, the present invention provides a process for the productionof a reinforced plastic article which comprises forming the articleeither in a mould or on a former from fibrous glass material bondedtogether by an unsaturated polyester resin laminating compositioncontaining a monomeric styrene compound characterised in that the mouldor former is made of a polymerised styrene compound and is adapted tobecome part of the produced reinforced plastic article.

Any suitable technique, such as those known in the art may be applied tothe formation of the reinforced plastic article in or on the mould orformer.

The fibrous glass material may take any suitable form such as mats,rovings or woven fabrics.

The laminating compositions used in the process of the present inventionare well known per se and may be of any suitable type which comprises anunsaturated polyester resin mixed with a. monomeric styrene compound. Byunsaturated polyester resin is meant throughout this specification aresin the molecules of which each contain at least 2 ester groups andtwo ethylenically unsaturated portions through which interpolymcrisationamong themselves and with the monomeric styrene compound may Suchunsaturated polyester resins are prepared by the interesterification ofsuitable dibasic or pol basic acids with suitable alcohols to givepolyesters in which either the alcoholic or the acidic portion thereofpossess the ethylenic unsaturation. One class of polyester resins may bederived from the esterification of saturated dibasic acids, such asphthalic acid, adipic acid, succinic acid or sebacic acid, withunsaturated alcohols such as allyl or substituted allyl alcohols.Another class of unsaturated polyester resins which is particularlyvaluable in the production of laminating or impregnatingcompositions-may be obtained by esterifying saturated polyhydricalcohols, such as ethylene glycol, diethylene glycol, trimethyleneglycol, 1,2-propylene glycol, 1:4-butylene glycol, 1:3-butylene glycoland glycerol with tat-unsaturated a,/8-dicarboxylic acids, such asmaleic, fun-laric, itaconic and citraconic acids. Suitable unsaturatedpolyester resins may be prepared from mixtures of the above polyhydricalcohols and unsaturated dicarboxylic acids. This type of unsaturatedpolyester resin may be modified by replacing some of the unsaturateddibasic acids with an equivalent quantity of a saturated acid, such assuccinic, adipic, sebacic, phthalic, azelaic, tetrahydlrophthalic orendomethylene tetrahydrophthalic acids.

The proportion of unsaturated polyester resin to mon0- meric styrenecompound in the production of such laminating compositions has beenwidely varied, but generally such compositions contain between 20 and byweight of the unsaturated polyester resin.

The mould or former used in the process of the present invention is madeof a polymerised styrene compound. Most suitably polymerised styrene isused either in the form of polystyrene or of a copolymer of styrene.Copolymers containing a major proportion of styrene and having a greatertoughness than polystyrene are particularly suitable for the process ofthe present invention. Styrene compounds may be copolymerised amongthemselves or with other monomeric compounds to produce copolymerssuitable for the production of moulds and formers. Such monomericcompounds include butadiene, isoprene, chloroprene, acrylonitrile andthe like. It is further possible to modify the polymerised styrenecompound from which the mould or former is to be made by the additionthereto of fillers and the like or by the t addition thereto of otherresinous products such as rubber;

The polymerised styrene compound may be formed into a mould or formersuitable for use in the process of the present invention by any of theconventional techniques applied to the formation of shaped articles fromstyrene compound polymers and copolymers. For instance, cast slabs of apolymerised styrene compound may be machined to the desired shape orthey may be cast in the desired shape in the first place. Alternativelythe polymerised styrene compound may be shaped by aconventional'pressure moulding, or injection moulding technique or anextrusion technique or by blowing a tube of the hot polymerised styrenecompound to the desired shape.

The mould or former used in the process of the present invention isadapted to become part of the produced reinforced plastic article and,therefore, it is generally made as light and as thin as possible havingregard for the strains to which it will be subjected during themanufacture-of the article. In this way the bulk and weight of theproduced article will be a minimum having regard to its mechanicalstrength which depends primarily upon the laminated fibrous glassportion thereof.

The process of the present invention can be particularly adapted for theproduction of reinforced plastic articles, such as conductors orcontainers, which have to withstand high fluid pressures. Such articles,as hitherto produced from fibrous glass material and suitable laminatingcompositions, although they have sufiicient mechanical strength, sufferfrom the disadvantage that they exhibit permeability to the highpressure liquids or gases contained therein. Polymerised styrenecompounds, on the other hand, are substantially impermeable to suchfluids and, therefore, if the mould or former is made from a polymerisedstyrene compound in such a. way that in the produced article the fluidunder pressure only contacts the polymerised styrene compound, theresultant article combines both the strength of the laminated fibrousglass and the impermeability of the polymerised styrene compound.

The reinforced plastic articles produced by the process of the presentinvention are particularly valuable and long-lasting in use because themould or former made from the polymerised styrene compound is integrallyattached to the bonded fibrous glass portion of the article. Thepresence of the monomeric styrene compound in the laminating compositionappears initially to soften the surfaces of the mould or former withwhich it comes into contact and thus when the laminating composition iscured to its final state it is integrally and possibly chemically bondedto the mould or former.

The following examples illustrate the production of reinforced plasticarticles by the process of the present invention.

Example 1 and 72 parts of maleic anhydride at 210 C. until theesterification was substantially complete (the acid value dropped to 35mg. KOH/gmJ.

This battery cell was extremely light and strong and was completelyimpervious to the sulphuric acid electro lyte used in the battery. Asimilar battery cell made from the same laminating composition on aconventional mould which was not incorporated in the final cell did notremain continuously impervious to the electrolyte in use. u

4 Example 2 Hollow laminated spheres to contain water under highpressure are formed on thin inner shells of polystyrene which have beenformed by injection moulding or by blowing from a hot extruded tube ofpolystyrene. The thin inner shell provides a male former around whichthe fibre glass laminated article is built up by wrapping a choppedglass fibre mat which had been impregnated with an unsaturated polyesterresin composition containing a curing catalyst. When the spheres havebeen built up to the desired size the polyester resin is allowed to cureunder the influence of the catalyst. The unsaturated polyester resincomposition was prepared by mixing 3 moles of maleic anhydride with 1mole of sebacic acid and 4 moles of diethylene glycol and heating themixture in a well stirred flask under an atmosphere of carbon dioxidefor 6 hours at 200 C. During this time water was evolved and the acidvalue fell to 30 to 40 mg. KOH/gm. The product was then allowed to cooland thinned with half its weight of styrene containing 500 parts permillion of tertiary butyl catechol (T. B. C.).

To parts of the resulting mixture was added 1 part of benzoyl peroxideand 0.1 part of dimethyl aniline as curing catalysts.

Example 3 Figures 1 and 2 illustrate a reinforced tube according to thepresent invention. Figure 1 is a perspective view of the tube and Figure2 is a diagram of its cross-section.

(1) is a polystyrene tube which has been formed by extrusion and (2) isthe bonded fibre glass reinforcement to the tube.

The reinforced tube is built up by wrapping the polystyrene tube with afibre glass fabric (Y.93 T.5 as manufactured by Fothergill and Harvey)which, just before application to the tube, is impregnated with alaminating composition similar to that employed in Example 1 andcontaining a curing catalyst. The impregnated glass cloth is woundaround the tube until the desired thickness is built up and the whole isset aside to cure.

In the appended claims, the term mold is intended to refer to a matrixon which the article is formed as well as a matrix in which the articleis formed.

We claim:

1. A process for the production of a fibrous glass reinforced plasticarticle, which comprises laminating a layer of a liquid unsaturatedpolyester resin composition containing fibrous glass reinforcement, amonomeric styrene compound and a curing catalyst therefor, onto aforming member consisting of a polymerized styrene, and bonding saidlayer to said forming member by polymerizing the layer to form a hardunitary plastic article of the desired shape, whereby the resultantpolymerized styrene in said layer is integrated with the polymerizedstyrene in said forming member and the latter constitutes an integralpart of the article produced.

2. A process as claimed in claim I, wherein the unsaturated polyesterresin of said unsaturated polyester resin composition is prepared by theinteresterification of an tat-unsaturated, a,;8-dicarboxy1ic acid and asaturated polyhydric alcohol.

3. A process as claimed in claim 2, wherein the unsaturated acid ismaleic acid and the polyhydric alcohol is selected from the groupconsisting of ethylene glycol, diethylene glycol, trimethylene glycol,1,2-propylene glycol, 1:4-butylene glycol and 1:3-butylene glycol.

4. A process as claimed in claim 1, wherein the monomeric styrenecompound is styrene.

5. A process as claimed in claim 1, wherein said forming member is madefrom a member of the group con- I 5 ester resin laminating compositioncontaining an initially monomeric styrene compound and a curing catalysttherefor and being directly integrated on one surface thereof with acorrespondingly shaped layer consisting of a polymerised styrenecompound.

7. A process as claimed in claim 1, wherein the said forming memberconsisting of a polystyrene is an inner shell around which the laminatedlayer is built up.

8. A shaped article as claimed in claim 6, wherein the said last-namedlayer is a discontinuous layer.

References Cited in the file of this patent UNITED STATES PATENTS1,985,997 Keeran Jan. 1, 1935 6 Burke Nov. 5, 1935 Keel-an June 16, 1936Lowry Dec. 17, 1940 Bailey Oct. 21, 1947 Schubert et a1 June 6, 1950Mohrman Dec. 19, 1950 Sutton May 13, 1952 Francis Oct. 14, 1952Ellenberger Mar. 10, 1953 Groff et a1 Sept. 3, 1957

1. A PROCESS FOR THE PRODUCTION OF A FIBROUS GLAS REINFORCED PLASTICARTICLE, WHICH LAMINATING A LAYER OF A LIQUID UNSATURATED POLYESTERRESIN COMPOSITION CONTAINING FIBROUS GLASS REINFORCEMENT, A MONOMERICSTYRENE COMPOUND AND A CURING CATALYST THEREFOR, ONTO A FORMING MEMBERCONSISTING OF A PLOYMERIZED STRYENE, AND BONDING SAID LAYER TO FORMINGMEMBER BY POLYMERIZING THE LAYER TO FORM A HARD UNITARY PLASTIC ARTICLEOF THE DESIRED SHAPE, WHEREBY THE RESLULTANT POLYMERIZED STYRENE IN SAIDLAYER IS INTEGRATED WITH THE POLYMERIZED STRENE IN SAID FORMING MEMBERAND THE LATTER CONSTITUTES AN INTEGRAL PART OF THE ARTICLE PRODUCED. 6.A SHAPED ARTICLE COMPRISING A BODY OF FIBROUS GLASS MATERIAL BONDEDTOGETHER BY A CURED UNSATURATED POLYESTER RESIN LAMINATING COMPOSITIONCONTAINING AN INITIALLY MONOMERIC STYRENE COMPOUND AND A CURING CATALYSTTHEREFOR AND BEING DIRECTLY INTEGRATED ON ONE SURFACE THEREOF WITH ACORRESPONDINLY SHAPED LAYER CONSISTING OF A POLYMERISED STYRENECOMPOUND.